If they have navigated to the page accidentally then they will have little idea of what it is that they`re looking at and they will likely leave before giving it enough of a chance. From a SEO (Search Engine Optimisation) point of view this can also be a bad thing as it takes the main `index.htm` file and neglects to put any content on it meaning it will be less likely to come up in the searches and the other pages will be less likely to be indexed.
Thus having a front page will potentially test the patience of your visitors, and will also potentially lower your ranking in the search engines. This makes it more suitable for particular types of websites and businesses than it is for others, so you should speak to your website design company about whether it would benefit you or not. A web design company will have a lot of experience obviously in designing their sites, and will be able to advise you appropriately.